1. Field of the Invention
The present invention relates to a bellows arrangement for a ventilator/anesthesia system of the type wherein the bellows arrangement has a rigid container in which a bellows is arranged, with a first end of the bellows fastened to one end of the container, and the second end being displaceable relative to the first end, and wherein the container can be attached to a propellant source and the bellows can be connected to a respiratory circuit at the aforementioned first end.
2. Description of the Prior Art
An anesthesia system with a bellows arrangement of the aforementioned type is illustrated and described in U.S. Pat. No. 5,678,540. The anesthesia system includes a respiratory circuit which can be connected to a patient, the aforementioned bellows arrangement, and a propellant source for controlling the flow of respiratory gas in the respiratory circuit. The interior of the bellows is connected to the respiratory circuit, as described above, and the space between the bellows and the wall of the container is connected to a propellant source.
For the initiation of an inhalation phase, the propellant source feeds a propellant to the space between the bellows and the container. When the pressure in this space is higher than the pressure in the bellows, the bellows begins to be compressed, causing respiratory gas to be fed to the patient. An exhalation phase follows an inhalation phase. During an exhalation phase, the propellant is released from the space between the bellows and the container, causing a relative pressure excess in the respiratory circuit and in the bellows to arise. The bellows then starts to expand, allowing the respiratory gas to flow out of the patient's lungs. This is repeated for each breathing cycle. Similar systems with bellows arrangements of this type are illustrated and described in published Swedish Application 466 635 and in European Application 0 557 134. Since the container is usually transparent, the movement sequence of the bellows is visible to the environment. In an expansion, or a compression, the bellows can wobble and/or its free end can end up in an oblique position, which does not affect the function, though it can disturb the hospital personnel.